Carbon nanotubes among diesel exhaust particles: real samples or contaminants?

Abstract

During three separate studies involving characterization of diesel particulate matter, carbon nanotubes (CNTs) were found among diesel exhaust particles sampled onto transmission electron microscopy (TEM) grids. During these studies, samples were collected from three different diesel engines at normal operating conditions with or without an iron catalyst (introduced as ferrocene) in the fuel. This paper is to report the authors' observation of CNTs among diesel exhaust particles, with the intent to stimulate awareness and further discussion regarding the formation mechanisms of CNTs during diesel combustion. Implications: Increased attention is being given to CNTs and other nanomaterials and a recent review paper showed that CNTs are capable of inflammation in the lung when inhaled. For this reason and because diesel engines are so common, it is important to acknowledge the existence of CNTs among diesel particles and possible regulation and online measurement method development.